The present invention relates to a device for separating a first liquid from a second liquid on which the first liquid is floating and, more particularly, to a skimming apparatus using a continuous flexible belt having an outer surface preferentially wettable by the first liquid.
Devices are well known for removing a first liquid, which is floating on the surface of a second liquid, from the second liquid. Such devices are used, for example, to reclaim oil from a mixture of oil or water. Alternatively, they are used to remove contaminants, including solid contaminants, from water which is to be reused. In either case, the device typically includes a belt or wheel having a surface preferentially wettable by the first liquid. One portion of the wheel or belt is typically disposed within the tank while the other portion is disposed remote from the tank. Various means are provided for removing the first liquid from the preferentially wettable surface.
For example, in Yahnke, U.S. Pat. No. 3,578,585, issued May 11, 1971, a porous polyurethane wheel is partially disposed within a tank containing water and is rotated about an axis disposed approximately at the surface level of the water. A roller is biased against a portion of the surface of the wheel disposed above the surface of the water so as to squeeze the oil drawn into the pores of the porous polyurethane wheel. The oil is then collected in a pan disposed below the roller.
A similar device is disclosed in U.S. Pat. No. 4,097,379, issued June 27, 1978 to Shelstad. In Shelstad, a porous drum is submerged in a tank of reclaimed water from a car wash installation. The porous drum is used as a filter to filter undesirable debris from the reclaimed wash water, which passes from the exterior to the interior of the drum. A roller is biased against an exterior surface portion of the drum, external of the tank, to squeeze the debris from the surface of the drum. The debris is collected in a tray disposed adjacent the roller. The tray is also provided with a scraping surface abutting a portion of the surface of the drum, to squeeze some of the surface water from the drum without removing the debris therefrom. The surface water removed by the scraper is permitted to flow back into the tank.
In U.S. Pat. No. 3,617,552, issued to Will on Nov. 2, 1971, an endless belt, formed of a series of layers of porous materials, is used to remove oil from a body of water. The endless belt is wound about exactly two spaced apart wheels. A front wheel is disposed below the surface of the body of water, while a second wheel is disposed above the surface of the body of water and to one side of the first wheel so that the portion of the endless belt which is being drawn out of the body of water is disposed at an angle of more than 90.degree. relative to the surface of the water, such as to facilitate the recovery of oil from the surface of the water. Furthermore, the water moves past the endless belt, or the endless belt is mounted so as to move through the body of water, to further facilitate recovery of the oil from the surface of the water. Two rollers are provided to twice squeeze the portion of the endless belt extended about the second wheel. The first roller gently squeezes the endless belt to remove water, the removed water being redirected downwardly into the body of water from which the oil is being removed. The second roller squeezes the belt vigorously to remove oil which is collected in a pan disposed below the second roller.
Still another device for separating oil from water using an endless belt is disclosed in Koller, U.S. Pat. No. 4,274,957 issued June 23, 1981. In Koller, a drive wheel is rotatably mounted in a housing disposed above the surface of a body of water containing surface oil. An endless belt, having a surface preferentially wettable by oil, is extended about the drive wheel and decends downwardly therefrom into the body of water. An idler roller is fitted to the lowermost end of the endless belt so as to maintain the endless belt in tension and to locate it directly under the housing. A pressure roller is rotatably and movably mounted to the housing at a location above the drive wheel so as to be biased downwardly by gravity against the drive wheel. The endless belt is thereby squeezed between the pressure roller and the drive wheel to squeeze oil removed from the tank by the endless belt from the body of water. The pressure roller is intentionally offset relative to the drive wheel so as to create a small trough of oil therebetween. The endless belt is designed to be substantially narrower than the drive wheel so that the oil may descend into a tray disposed below the drive wheel.
Each of the above described devices have certain advantages and certain disadvantages for various applications. For example, while Will removes a substantial amount of oil from water at a comparatively rapid rate, it is a rather complex and large device and is, therefore, inappropriate for many applications involving small tanks. Similarly, while Koller provides a comparatively compact device, a substantial amount of operating time is required to remove a significant amount of oil from water using the device disclosed or taught thereby. While the remaining above described devices may work well for the purposes for which they were designed, none of these other prior devices function well for removing oil, for reclaimation purposes, from the surface of a body of water.
What is needed, therefore, is a lightweight, but efficient, oil skimmer for removing oil or other lightweight liquid contaminants from the surface of a body of water.